In the production of silicon wafers for use in integrated circuit manufacturing, a final step is the polishing of the wafer surface with very fine abrasive particles carried in a water solution. The water which is used for this solution typically is obtained from de-ionization, reverse osmosis systems. As a consequence, the water used in the abrasive slurry is quite expensive; and large quantities are used. If a substantial portion of this expensive water can be recovered and re-used, it is worth the effort, both from the saving of the initial feed water itself, as well as savings in the RO/DI process.
Systems have been developed in an effort to improve the efficiency of wafer polishing systems. The U.S. patent to Russ U.S. Pat. No. 6,244,929 is directed to a polishing system with continuous filtration. In order to accomplish the continuous filtration, two parallel filtration paths are employed. At any given time, one of the paths is used to receive slurry from a reservoir and supply it to a polisher. Simultaneously, the other path is backflushed, with the backflush being obtained from a de-ionized water supply and then diverted to a drain. At periodic intervals, the valves are switched; so that the newly backflushed side then is used to provide slurry from the reservoir to the polisher, while the other side is being backflushed. There is no showing of re-use of effluent after the polishing operation under the control of any sensors.
The U.S. patent to Pinder No. 5,895,315 is directed to a recovery device for a polishing agent and de-ionizing water for a polishing machine. The system of this patent, however, does not employ any effluent sensing to control the recovery of any of the materials used in the system. All switching of the valves is accomplished through the electronic control unit, which receives signals from the polishing machine itself. Effluent sensing, however, is neither disclosed nor discussed in the Pinder patent.
The U.S. patents to Hayashi U.S. Pat. No. 5,647,989; Adams U.S. Pat. No. 5,664,990; Toyama U.S. Pat. No. 6,001,265; Katsumata U.S. Pat. No. 6,161,533; and Zavattari U.S. Pat. No. 6,231,628 all are directed to slurry recycling or recovery and separation. None of these patents, however, use any sensors for sensing the condition of an effluent on a continuous basis to switch or divert the effluent from one output to another, as determined by the clarity or other chemical condition of the effluent.
A system has been developed for diverting effluent from a silicon wafer polishing process to either a dirty output or a clean output for appropriate further processing. This system employs a sensor at the input side of a diverter valve to determine the xe2x80x9cclearxe2x80x9d or xe2x80x9cdirtyxe2x80x9d condition of the effluent. A signal from the sensor then is utilized to operate the diverter valve accordingly. As a backup, a second process sensor is located on the xe2x80x9ccleanxe2x80x9d or clear water output side; so that if any xe2x80x9cdirtyxe2x80x9d effluent reaches the clean side when the valve is switched to divert effluent to the clean side, the valve then is switched to divert the effluent to the dirty side. Because of the locations of these sensors, however, it is possible for short bursts of xe2x80x9cdirtyxe2x80x9d effluent to reach the xe2x80x9ccleanxe2x80x9d side of the diverter valve when the condition of the effluent in the input side of the valve changes.
Accordingly, it is desirable to provide a fluid diversion system, particularly suitable for utilization with the effluent from a wafer polishing system, which overcomes the disadvantages of the prior art, and which ensures accurate diversion of clean water to a reclamation outlet.
It is an object of this invention to provide an improved fluid diversion system and method.
It is another object of this invention to provide an improved waste water diversion system and method.
It is an additional object of this invention to provide an improved waste water diversion and recovery system and method.
It is a further object of this invention to provide an improved waste water diversion and recovery system for the recovery of recyclable waste water from effluent from industrial processing operations.
In accordance with a preferred embodiment of this invention, a fluid waste diversion system and method is supplied with a source of fluid effluent. A diverter valve has an input coupled to receive the fluid effluent; and this valve is operated to divert the fluid from the effluent to one or the other of first and second outputs. Fluid parameter sensors are placed to sense particular parameters of the fluid supplied to the input of the diverter valve and to sense particular fluid parameters from the fluid supplied to the first output. The diverter valve initially is set to supply fluid to the first output. When the signals from the sensors simultaneously indicate a predetermined condition of the sensed parameters, a control circuit is operated to switch the diverter valve to supply the effluent to the second output. At any time one or the other or both of the sensors indicates that the predetermined parameter conditions are not met, the valve is switched back to the original condition supplying the effluent from its input to the first output.